Catalytic cracking-isomerization alkylation process



Oct. 2, 1,945. A FOSTER I 2,385,806

CATALYTIC CRACKING-`ISOMERIZATION ALKYLATION PROCESS :Filed Feb. 1e, 1942 ALKYLATE Nollv'lm-w OLEFIN ISOMER RECYCLE NOILVZIHIIWOSI SPENT l CATALYST lNvNToR ARcH- 1 Pos1-ER Patented Oct. 2, 1945 CATALYTIC CRACKING-ISOMERIZATION i ALKYLATION PROCESS Arch L.` Foster, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application February 16, 1942, Serial No. 431,174 l 7 Claims.

My invention relates'to an improved process of. hydrocarbon conversion. Ina specific aspectl it relates to a process of making hydrocarbons boiling in the motor and aviation fuel range. One particular embodiment has reference to a process including the steps of cracking heavy oils, i. e., petroleumoils boiling above the motorA or aviation fuel range to produce a maximum of C2 to Ce paraiiinie hydrocarbons, isomerizing resulting parafns of four to six carbon atoms per molecule to isoparamns and yalkylating these isoparamns with oleiins from an outside source, and using the same catalyst in the steps of the system in a diierent sequence from that followed by the charge stockin such manner that'it is used in steps of 'progressively increasing severity.

The production of motor and aviation fuel components in an efficient and economical manu ner has been a problem of great difficulty. Prior practices have involved Vthe use of a plurality oi.' unrelated steps carried outl separately and inemciently in different plants or in different locations. Costs have been excessive because of the ineiiiciency and nonlunitary nature of previous processes.y My process 'aims to markedly reduce and are being used in commercial processes. In all these processes, especially in those employing thermal methods alone, a large percentage of the charge stocks is converted to gaseous hydrocarbons and light materials too volatile to be used satisfactorily in motor and aviation fuels.

Thermal and catalytic processes as normally opthese high costs and increase eiiiciency by pro viding a unitary process of obtaining these high. octanehighly branched paraflln hydrocarbons from crude raw material and inwhich the several steps are uniquely inter-related in a. new and unexpectedly eiiicient manner, and in which a single catalyst is used in the several different steps of the process without intermediate reactivation or regeneration.

'I'his invention relates generally to the treatment of hydrocarbon oils to produce oils more" directly adapted to purposes more useful than those to which the original oil may be applied. More specifically it relates to the conversion of heavy oils or of light fractions of lower molecular weight and anti-knock properties to superior fuels of very high anti-knock characteristics and ofthe desired-volatility and vapor pressure required by modern automotive and aviation engines. These desirable results are obtained by a series of catalytic steps, whereby the desired products are obtained in a new and novel manmeeting with 'more or less exaotness the specifi=" cations for boiling range ,of motor gasoline. The anti-knock properties of these distillates, whiie often greatly improved over those of the straightrun gasoline from the crude are not satisfactory for use in aviation and similar fuels requiring especially high octane number characteristics. The unsaturated nature of these products also makes them unsuitabie for aviation fuel pur-- posesr Addition of hydrogen to saturate these molecules is a process well known in the art, but

is expensive, and generally reduces the antiknock tendencies of the hydrogenated'prduct. Furthermore, in the distillation, cracking and rening of crude petroleum and its fractions ner and more economically than has been pracy ticed in the art heretofore.,A

The conversion of heavier hydrocarbons of petroleum by thermal means into lighter prod-v varying amounts of saturated and unsaturated light hydrocarbons, including those containing one to six carbon atoms, are formed. vLoss-of these hydrocarbons `or any substantial part of them reduces seriously the efliciency and the yields in rening petroleum, and methods of utilization of these Icy-products and of converting them to useiul materials improves both the n economy of refining and the quality of. the prod` uots made.

.'I'hepercentageof these waste hydrocarbons is contingent on the conditions of operation of the processes in which they are formed, and the quantity produced in any rennery at diierent times vmay vary widely. Operationof' a process employing these waste products asraw material would be hindered `or made impracticable if deinclude means in the process which can supply all the raw material required for the capacity of the process unit, and to add toj the charge material from this source such light hydrocar- The more satisfactory methodis to' then be discarded as of no further value.

ever, Ihave discovered that the catalysts recomerated nearby, the use of these waste hydrocarbons being in the nature of auxiliary supply relieving the demands on the primary source of charge stock in the process with which this in- V vention deals. Variation in quantity ofsach auxiliary-produced charge stocks available can thus be smoothed out by varying'at will they amounts produced from the primary source, the first or cracking step in the invention discussed below. Variation in composition of such auxiliary charge material may be obviated within reasonable limits by change in the manner and conditions of operation ofthe step employed as source of the primary supply of raw material for the succeeding steps of this invention. Thernet result of providing against all such variations in quantity and quality is to insure that the economics andfthe efficiency of. the process of this invention are satisfactory and therefore that its commercial success is assured within any reasonable limits.

Another of the factors on which the technical and commercial success of a catalytic process depends is'economy and efliciency in the use of catalysts. Catalysts, such as those mentioned herein, are efiicient for a .given purpose under the conditions employedfor a given throughput or length of time, and' then are said to be exhausted, to require regeneration or which must Howmendedy herein, after having spent their' effect in, 'one step of the process, are extremely useful.

and eflicient.in other steps under different operating conditions and to effect different results. vlit vis therefore practicable to employ thesecatalysts in successive steps inthe process, and by such repeated employment to make eachstelll` more'eiiicient thanit can be made in any other manner, and to utilize the catalyst to a much higher degree of efficiency than has been hereto fore practised in the art. The sequence of steps and of operating conditions ,to which the catalyst is subjected is so arranged`that,when the catalysts activity is exhausted at one temperature, pressure or contact rate and because of which 'exhaustion its emciency in effecting a given reaction is reduced below'a satisfactory level, its activity is somewhat restored and it becomes satisfactory -for effecting another reaction under vdifferent operating conditions when catalyzing another reaction between or upon other charge stocks orraw materials. An eiiicient arrangement of the sequence of 'these steps and of the employment of the catalyst in them, arranging the operating conditions so as to promote to the greatest degree the efliciency of the Acatalyst and of the reactions which are effected by it in turn,

' are very important factors inthe invention and are an essential part thereof. y y

`The essential arrangement of these steps and of the reaction conditions employed in each step insequence have beenl so determined that the results obtained in each step` and the composite result of they entireV process is higher efficiency in product yield and product quality than is obtainable by any other procedure Aknown to'v the prior art. 1 .v

vOne object of ,this invention, therefore, is to obtain higher efficiency-inthe useof. catalysts v than has beenv obtained heretofore. v This higher f efliciency is obtained by utilizing` the/catalyst or catalysts under different conditions in a series of stepsv which constitute a' major.` part ofthe bons as may be produced by other processes opl invention, each step so conditioned and operated that;the optimum results in that step are obtained, the catalyst is used to the optimum degree and is left in such condition as to be most efficient in thenext step of the process. This method insures the greatest economy in operation of the process, in which economy of operation is one of the essentials for its success. l

` -Another object oi the invention is to convert heavy oils, unsuitable for-fuels in spark-ignition K engines of any type commercially operated now, into fuels of lower. average molecular weight, 'higher'volatility and of greatly increased antiknock values `by a process of higher technical results required in the process or a combination o f two oi" more of these disadvantages. This so invention obviates these disadvantages lin turn, producing a premium quality product from waste and/or low grade 'raw materials with the best economy, at the same time utilizing one of the most essential elements of=the process, the .catalyst, to the highest degree of vemciency.

" Still another object of this invention is the utilization of otherwise waste or light. normally 1 Vgaseous hydrocarbons vformed. in otherY refinery processes such as thermal or`- catalytic cracking llas intermediates for the manufacture of thesev `super-quality fuels. This object represents a definite conservation of natural resources andv van improvement in the overall efiiciency of the `reiining of petroleum. It also increases the ,45 amount of these superior fuels produced. from any given quantity of raw material.

Another object of this invention is the utiliza- `tion of light normally gaseous hydrocarbons which may be obtained in the manufacture of -natural gasoline'but which possess'too' high volatility for `,use as such in motor or aviation fuels in any great amount. Conversion of these hydrocarbons fto usable 'products is also a conservation feature of the process vital t0 the industry and to economy `in the use of natural resources, at the same time contributing to the production of super-fuels highlynecessary in our national development.

4exhaust-the advantages nor the purposes of it,

nor are its purposes and objects confined to those mentioned, which are to be considered as typical `examples `of its usefulness in application to the technology of the art. Other objects and advantagesy will become apparent in the specifica-l tions and claims which'follow. v

' In accordance with my invention in one form,

` a catalyst, in slurry or other form which permits ,l

it to flow from place to place, is circulated through.

an individual reactionvzone continuously until its reactivity in that step is exhausted; is then 4severe operating conditions wherein its reactivity is greatly increased for the purpose of the new reaction: and is circulated therein 'until its ,re-

activity for that reaction is exhausted; and is These several objects of the invention do not I transferredto another reaction zone unde/r more closure.

per molecule. (2) these hydrocarbons are molecularly rearranged to produce isomeric paraflins of more complexv structure. (.3) the resulting hydrocarbons are alkylated with olefins under optimumvconditionfs for this reaction, to form more complex molecules boiling in the motor and aviation fuel range.

' Arranged sequentially with respect to the path of the catalyst, or its use, the steps of my invention are; first the isomerization step wherein temperatures and pressures are the mildest of -the three steps, next the alkylation step wherein more severe conditions prevail, and finally the cracking step wherein still more drastic conditions of temperature and pressure are used.

The catalyst need not be in slurry or pumpable form, transferred from zone to zone. On the contrary, it may be asolid, in situ, and by a system of manifolding of the reaction chambers the charge material to each step may be switched so that the same sequence of conditions and re,- actions are effected inv the same tower. Thus the principle of a succession of reactions destinedto convert heavy oils into highly branched-chain hydrocarbons of high anti-knock rating and volatilities suitable for motor and aviation fuels, with the same catalyst under` conditions suitable for each o f the three main reactionsis applied in this variation.

The catalyst is employed iirst in the isomerization step, wherein temperatures and pressures are the mildest used in the process; when its reactivity is exhausted under those conditions, temperatures and/or pressures are increased to values at which its reactivityis somewhat restored and is vsatisfactory for promoting the alkylation reaction; when its reactivity is ex, bausted for use in this step, temperatures and/or pressures are raised to values which somewhatrestore the reactivity -of the catalyst and which are satisfactory for its use in cracking heavy oils to produce paraffin hydrocarbons of two to six carbon atoms per molecule in maximum yield.

I believe that the combination of the steps of cracking, isomerizing; and alkylating in succession in a singlel closed system with the same catalyst under diiering conditions is new. ThisV process enables the operator to effect increases in yields, to 4pass material from any one step to any other step to produce the maximum yields or maximum conversion with resultant economies in heating, pumping and other attendant steps in the process, and to obtain results, formerly obtained in separate steps at the expense of economies of cost and of productionA eiciency, at the lowestcost andmaximum eiiiciency in utilization of 4raw charge stock and of catalyst with a minimum of separate steps. Numerous other advantages of the present invention will be apparent ,-to those skilled in the art from a consideration of the following detailed dis The purpose -of this invention is accomplished-- by the decomposition, by catalytic means, of

heavy oils to produce a maximum yield of satu- I rated hydrocarbons containing two to six carbon atoms per molecule; by effecting catalytically a rearrangement of the molecular structure lof these light hydrocarbons which have at least four carbon atoms per molecule to form branched-chain molecules' from normal or straight-chain hydrocarbons and. more lhighly branched structures from the simpler branchedchain types; by combining catalytically these branched-chain hydrocarbons with olefinic light vhydrocarbons of the same or a diierent number of carbon atoms per molecule, to produce still more highly complex branched-chain hydrocarbons of extremely high anti-knock properties and' of the desired volatility required in automotive and aviationv fuels, or forany other purpose for which these properties are particularly suitable. The terms heavy oils as used above is dened to include any hydrocarbon material the lowest molecular-weight of the components of whichpresent in substantial quantities, is greater than the molecular weight desired in the products from the first step in the invention as described below.

It is well known in the art that heavier hydrocarbons under the influence of catalyst suitedto "the purpose maybe decomposed to hydrocarbons straight-chain structurev or those of th'e simpler branched-chain or isometric structure.

'Ihe catalysts employedy in the rst step of this `invention produce the saturated hydrocarbons under the conditions described and it is to such catalysts that reference is made herein when the term catalyst is employed in describing the first step.

It is also known to the art' that. straight-chain and/or the simpler branched chain hydrocarbons undergo a molecular rearrangement when treated with the proper catalysts, forming hydrocarbons of more intricately branched structures.

The second step in this invention accomplishes l this molecular rearrangement reaction to prepare the type of highly branched paraiiin hydrocarbons required in the third step, from vthose formed in the rst step. These several steps may be accomplished by the use of the same or difierent catalysts in each reaction step. It is preferable, to obtain the full advantage of this invention, to employ certain catalysts', such' as metallic halides in various physical forms, under differing operating conditions, using the same catalyst to effect each of the three steps which constitute this invention. y

It is also known that, under suitable reaction conditions and with the necessary catalysts, branched-chain paraffins will unitewith either straightor branched-chain olefins in such manner as to form a larger molecule, chieiiy the type of molecule the weight of which is the sum of the molecular weights of the reacting hydrocarbons. By carrying out this reaction in the thirdstep of this invention, a reaction between the branchedchain hydrocarbons obtained as a result of the second step and oleiinic hydrocarbons containing twol .to six or a higher number-.of carbon atoms per molecule, the iinal product of .this process and invention'is composed of hydrocarbons of range of combinations.

l catalyst, etc., either for reasons ofthe nature of the lproducts desired or of the properties of the raw materials mosteasily or economicallyavailable, for both or for-other reasons. Differences in the characteristics of charge stocks, in the nature of the catalyst or in its mode of preparation or use, or in the composition ofthe product from any step in the process as may be desirable,

' or in the composition desired in thc nished principles set forth herein.

product, and in'any or all of these considerations may dictate changes in conditions or vice versa.

Changes in any'or all of these factors will eectv changes in the results obtained. The effect or variationsin process details will be apparentto those skilled` in the` art, and experience in operation of a given unit for the application of this process to any desired purpose or with any combination of raw materials will inform the skilled'.

operatorr of the effect different conditions will have upon the products made and on the econvonly of the process. f Nor under any circumstances are the examples here given'of the operation of the process to be considered as exhaustingthe possibilities or `setting exact limits to theinvention. These'examples are for the express purpose ofyshowing how the principles on which the invention is based may be applied tothe preparation of superior products by the most novel and economicalprocess incfuded in the invention.

Following'is a description of 'how the principles of this invention may be applied in-practice. Many variations of this method of application may be used4 to obtain the desired results. Differences in the nature andv properties of the raw materal anddiiferences desired in the finished products will dictate changes in operating conditions which will be well within'the limits of the invention and which will yapply the In accordance withl my invention, in -its broadest aspect, a petroleum hydrocarbon raw material is subjected to at least two diierent catalytic conversion operations of fundamentally the subsequent alkylation step in the process,-y

under relatively severe conditions to form substantial quantities of Ci to Cs paraiin hydrocarbons, and alkylating said C4 to Ce paraflins either as such, or the highly branched contentthereof,

or preferably after a catalytic isomerization step to convert the normal parailin content thereof and/or the less highly branched paraflin content' thereofv to the most highly branched isomers which are most desirable for-alkylation. The

. same metal halide catalyst is used in the alkylation step, it being used for the cracking ste'p after f it has become spent for said alkylation step. Reacton conditions for the alkylation step which are substantially less Asevere -than those in the cracking step are maintained, land although the catalyst be substantially spent for the alkylation stepthe more severe cracking conditions cause it to be highly active for the cracking step.

In another embodiment, my invention mayo comprise rsubjecting a petroleum oil ranging from naphtha to heavy gas oil to cracking .over a 4metal halide catalyst preferably aluminum chloride in anhydrous form which has been spent for a subsequent isomerization step, under relatively severe conditions to form substantial quantities of C4 to Cs parailinl hydrocarbons, and `isomerizing the normal paraiiin content of said C4 to Cs paramn hydrocarbons and/orthe less highly branched paraiiln'content thereof to the most highly branchedr isomers. l The same metal halide catalyst is used in the isomerization step, it being used for the cracking step after it has become spent for said isomerization step. Reaction conditions for the isomerization `step which are substantially less severe than those inthe cracking step are maintained, and

although the catalystfis substantially spent for theisomerizatio step the more severe conditions maintained for Ithe cracking cause itgto .be highly active for said cracking step.A

Ina still more specific embodimentthe present v i invention comprisesY subjecting a petroleum oil ranging from naphtha to heavy gas oil to cracking over 'a metal halide catalystsuch .as anhydraus aluminum chloride which has been spent for a subsequent alkylation step, underrelatively severe conditions to form substantial quantities of C4 to Cs vparailin hydrocarbons, subjecting to catalytic isomerization the normal parailin content of said C4 to Cs paramn hydrocarbons and/or different type in sequence, in which reaction conl ditions of 'substantially differing severityv are maintained, such as for example; cracking and isomerization; cracking andalkylation; isomerization and alkylation; cracking, isomerization and alkylation; etc. The same metal halide catalyst, preferably anhydrous aluminum chloride, is used in the' different operations`,vbeing used rst in the less severe or more mild operation, usually until its reactivityv for that reaction is substantially spent, and is then used in the more severe operation. By using thesame catalyst in conversion steps ,in which progressively more severe conversion conditions are maintained, the catalystwhich is spent for a preceding'conversion step is lrendered,sufficiently"'active for theV next conversion step and'great economies are eifected.

In a morespecflc aspect, my invention com.

prises subjecting a petroleum oilranging from naphtha to heavy gasv oil to cracking 'over a metal halide catalyst preferably aluminum chlo-v ride inf'anhydrous form which has been spent for the less highly branched paraffin content thereof to form the most highly branched isomers, under relatively mild conditions with fresh solid metal' halide catalyst which is the same asl that usedy in the cracking step, and subjecting the most highly branched isomers -to alkylation under conditions more severe than for said isomerization and less severe than for said cracking step using as catalyst the spent catalyst from said isomerization step.

The cracking step may heating the cracking feed in suitable equipment up to a temperature of from about 600 to about 800 F. and passing it at this temperature in either the liquid or vaporized form depending fupon the feed, the temperature and the pressure, and at a pressure of from about 200 to about 500 i pounds perA square inchthrough a suitable reaction vesselwhere it intimately contacts the metal i halide catalyst. Sumciently drastic cracking conditlons, i. e. temperature, pressure and contact time, are employed to give the desired cracking l reaction; with the. spent Icatalyst from the alkylation step or the isomerization step. The selection 4be conducted by preweight. v

If the charge is introduced in vapor form -no of pressure, temperature, and contact time will depend upon the lspecific charge stock being `treated andthe specifications of the products desired li'rorm the cracking step, and will be obvious to those skilled in the art in the light of this disclosure. The metal halide vcatalyst may be'employed either as a slurry, or sludge as obtained from the second or thirdmain steps of my process or may be in situ inthe tower in solid form and on any convenient supporting means ii' desired.

If the slurry or sludge form of catalyst is `employed, it is pumped into the cracking tower at a point below the topvof the tower and preferably below the point of exit of the charge stock if the latter is in the liquid state. The catalyst is also preheated to the reaction temperature and-the tower is heated by external means to 'maintain the desired temperature or temperature gradient throughout the reaction zone. The towervmay also be equipped with perforated or solid baiiles tions to yield the desired type of product may easily be determined by the skilled operator lfor any given charge stock or combination of stocks. If desired the lighter products formed during the reaction maybe vaporized and freed from liquid `or solid matter in the upper part of the tower, which space is maintained as a flash space free of liquid or solid material and in which a suitable baille arrangement may be placed to knock back any solid` or liquid entrained material. The eiiluent will contain the 'C2 to Ca hydrocarbons aswell as'any lighter and heavy material which may be vaporized at the temperatures and pressures employed and any solid, liquid or vaf porized catalyst. 'I'hese vapors after separation of entrained catalyst are rectified in conventional fractionating equipment. the lighter products going to the plant vapor recovery u nit or to any other desired point such as a dehydrogenating unit. The heavier incompletely cracked material is recycled to the cracking step mixed with the fresh charge for further reduction in molecular charge liquid will be present to be discharged from the cracking tower. If in .liquid form the residue of the charge is drawn oil, the vapor is passed into a knock-out box to remove any entrained or volatilized catalyst and discharged into the fractionating' tower. If the same fractionating tower' is used for both overhead vapors and liquid residue the liquid may enter the tower at a point below that where the vapors enter. In

the latter case the liquid residue is 4stripped of desirable lighter components. and withdrawn from the tower bottom. Recycle stock may be drawn from a point higher in the same tower as a side stream. The rectified vapors poss overhead i'rom this tower, are preheated if necessary and enter the second .step oi' the process. l

Another variation of this part or the process temperature, etc. mayy be varied so that the product is obtained in two or more streams. For example, by the employment of one or more additional fractionating towers, individual hydrocarbons may be isolated and in turn eachmay be Vfed to individual separate units -in the j next step in the process. Or, for example, theCa to C; fraction may be taken overhead from .the main tower, while the C5 to Cs fraction may be drawn off as a side stream and fed to the next step in the process separately from the lighter fraction.

In a modification, the fractionation of the cracking effluent may beso conducted as to yield two separate fractions of C4 to Cs hydrocarbons, oneof which-consists of the most highly branchedl parafllns which may be passed around theisomerization step to the alkylation step, and the other of which consists of the less highly branched i and straight chain paraillns which may be passed into the isomerization unit. In this way more effective isomerization is effected since the presence of the most highlybranched isomers in the isomerization feed would tend to prevent conversio'n of less highly branched forms to such isomers by reason of their already high concentration, in

consequence of the law of mass action.

Another variation of the process is the use of the catalyst in solid form. In this case the catalyst may be pelleted, briquetted with or without an inert carrier or deposited on a solid inert carrier. Thus the catalyst may be placed in the reaction towers, supported in any convenient manner, as on wire screens,perforated plates or merely stacked in the towers to the desired level.

Cracking conditions are so maintainedgwith any given charge that thetotal conversion to lighter Ahydrocarbons is not less than about 10 percent to not more than about 50 percent of the charge; Percentage of the different hydrocarbons vary with varying reaction conditions, but a typical composition of the eilluent vapors from thereaction zone is: ethane, 2-5%; propane,.415%;

butanes, 20-50%; pentanes, V12-?f0%; hexanes, 520%; small amounts of heavier material to be recycled; and also small amounts of methane. Still more severe temperatures and pressures tend to produce larger proportions of the lighter hydrocarbons of relatively simple structure. More rapid throughputand shorter contact time, with vless severe temperatures and pressures 'produce a larger proportion of the pentanes and hexanes with somewhat more branched-chain structure.

The products from the cracking step are highly saturated in character, containing little,if Vany oleilns and are chiefly normal and simpler branched-chain pro/ducts.` 'I'he ethane and propane in the exit vapors are segregated by fractionationV in a suitable low temperature tower from the remainder of the vapors, which latter preferably are at the same time separated intov r,

- individual hydrocarbon streams, or may be removedl in a single fraction for further treatment as described later.. -In the event that multiple streams of product are obtained by multiple fractionation tosegregate hydrocarbons of essentially the same molecular weight in individual streams,

. it is practicable to further fractionate each of Y scribed below. and

these streams to separate the normal from the lbranched-chain parailins in each stream. The

branched-chain fraction of each stream may then by-pass the second or isomerization. step, de-

the charge tothe third or alkylation step, also described bellow, either blended into one stream is that fractionation tower conditions of reflux.' 7 or treated in individual reaction vessels as desired.

may be used directly as part ot Generally, however, it is preferable to transfer the lentire product from the first step (i. e., the

'entire'Cr to Cs paraflinr portion) directly to the products or those from natural gasoline recovery plants. 'I'hese outside hydrocarbons may be conl A centrated to the same degree as the streams lfrom the cracking or decomposition reaction and correspond to their qualitative composition.

-The vapor and/or liquid stream or streams an isomerization unit where fresh catalyst either in slurry or solid form is encountered. If in slurry form the catalyst may be made up in any convenient manner as with oil from the charge stock to the flrst step or with a portionof the charge of C4 to Ce parafhns' to the isomerization step itself. If solid it may be in any form such Y may be operated in series to extend the `reaction v fromthe cracking s tep are now introduced into about90% of the charge is converted per pass tol time `to any desired length.4 The catalyst is pre- 'heated to the reactiontemperaturedesired and the isomerization toweris also heated to maintain the requiredl 4temperature or temperature gradient to achieve optimum results. If a plu-v rality of streams is treated vin the isomerizaev tion step .the operation of each follows essentially the principles outlined above. f

Treated vapors from the isomerization unit' enter a fractionating tower or towers, after passing through one or morev knock-out boxes to rel move entrained or volatilized catalyst. lIn the fractionating isystem the hydrocarbons ofmore ,complex (more highly branched) structure, are

passed overheadwhile the normal, straight-chain rhydrocarbons are recovered from the bottom of the tower and `returned as recycle to be mixed Vwith the fresh charge.

' Operating conditions in the isomerization system are maintained such that from about 20 to hydrocarbons of more'complex structure, the optimum conversion rate per pass being determinedby the requirements of the final 'or end as indicated above for the rst or cracking step or in any other form convenient or efllcient for the purpose. The step described here will include `only that variation employing the slurry catalyst form, but the principle of the invention is applied as easily and efllciently-when using solid catalyst kor a combination of solid and liquid catalyst, and

these Aother modifications yare included in the vscope of this invention. v

The charge stock to the second or molecular rearrangement step is heated if necessary to from about 75 to about 425 F. and pressuresl enter the isomerization tower.

pounds per sq. in. are employed. .The charge may If a plurality `of streams are treated, in separate reaction towers. more severe temperatures and pressures may be y-to the amount of'fresh catalyst addedmay be continuously drawn off and transferred tothethird lstep in the process. An auxiliary catalyst or catalyst promoter, such as a hydrogen halide such as anhydrous hydrogen chloride, to the extent of from 1 to about 10% by weight based on` lfrom substantially atmospheric to about '350 maintained for the more refractory streams than' for the less refractory in order to obtain a satisthe' weight of the ,charge ispreferablyadmixed with the incoming. vapors immediately prior to their entrance into the reaction tower. Recycle containing normal hydrocarbons recovered from the isomerization eil'luent may also be mixed withv l the fresh charge. The reaction tower may be equipped with a series of horizontal perforatedplates, or other means for breaking up the stream of' incoming vapor to prevent its passing up through the catalyst yin large unbroken volumes,

or channeling with consequentpoor contact with the catalyst.v The time of contact may be varied at willby regulating the rate of introduction of charge. `If the requirements of the nal product products and by the composition ofthe charge.

The branched-chain hydrocarbons overhead from the isomerization step fractionator system pass to the third or alkylation step of the process,

being preheated, preferablywithout prior condensation toa temperature of from about 300 to about 600 F. under pressure of from about 15 to about 500 pounds per sq. in. prior to entry into the alkylation unit which may be operated under said conditions of temperature and pressure. The

" @example from abouti toiabout 10%by' weight chargemay enterlthe bottom of the alkylationv tower. Where a plurality of streams of-C4 to Cs iso-paraflins are being Valkylated, separate alkyla` source are introduced into the alkylation tower,` y preferably at a plurality" of points. Thepropor' tion of olefins introduced into the tower at any instantshould notexceed about 10% ofthe iso- `paraflin present. The olenns are introduced at intervals spaced so that the vvoleiiln-paraflln yratio is so small that polymerization of the olen is substantially precluded and the desired alkylation reaction between isoparamn andjolefln is promoted to the optimum degree. `The olens are preheated to some temperature not higher than the reaction temperature in the tower but below the temperature where appreciable polymerization takes place. Preferably a small increment of the olen-is mixed with the isporaratlln charge immediately prior to itsentrance'into the tower.

In addition it is desirable to introduce a small lamount .of anhydrous hydrogen halide such as hydrogen 'chloride tothe alkylation unit. .For

based on the weight ofthe charge may be admixed with the incoming vapors immediately prior to their-entrance into the alkylation tower.

Catalyst may be circulated continuously through theel-mation tower, entering at' .the top` and making exit atthe bottom, a portion 'of the a longer contact time than is pracvobtained from a source outside my process.

aasaeoe exiting used catalyst being withdrawn continuously and a corresponding amount of spent isomerization catalyst being added to maintain the system constant. 'I'he tower may be fitted with a system of horizontal or sloped baiiies, either percatalyst is heated by auxiliary means before entrance to the reaction zone, and the tower is also heated, or insulated, in any suitable manner to maintain the desired temperature or temperature gradient in the reaction zone. This ternperature may be varied within the above limits depending on the feed, the specic properties of the desired product and the'other'operating conditions employed.

The olen material employed in the alkylation may be obtained from any convenient source, and

this source may be varied at the will of the op. erator. Olefins may be derived from cracked still' gases, concentrated to obtain adequate amounts of oleiins from ethylene to hexylenes or any desired mixture of these hydrocarbons.

Olens may be derived from the thermal or cat' alytic dehydrogenation of .parain hydrocarbons A portion of the normal paraiiins produced in the cracking step of my process may be diverted to a dehydrogenation step instead of being passed to the isomerization unit. Hydrocarbons of the required number of carbon atoms may be obtained from a source such as refinery or natural gas or gasoline and dehydrogenated to give the necessary oleii'ns.

In the alkylation zone operating conditions are s0 maintained that no substantial amount of olens remain unreacted as the vapors exit from this zone. The various control means available to maintain this condition of substantially complete reaction of the oleiins introduced to the alkylal tion unit are obvious. to thoseskilled in the art.

The alkylation reaction vapors are led through a knock-out box'for removal of entrained or volatilized catalyst and then to a fractionator where unreacted hydrocarbons are separated from the alkylate and are returned as recycle to be blended with `the fresh charge. The alkylate, being high-boiling, is drawn oil either at the bottom of the tower as a, single stream or as one or more side streams in addition to a bottom stream,

and is removed from the system for any further desired treatment orto storage.

The yield of total alkylate from a given stream may be from about 125 to about 200% or more based on the weight of olefin charged to the sys- /or more steps. step of'myprocess may be brought into contact invention I generally use aluminum chloride as most eective and economical. However, I may use anhydrous metal halides generally such as the chloride, bromide or iodide of such amphoteric ,metals as ,aliuninunn zinc, tin (stannic) titanium (tetrachloride), antimony (antimonic), ironV- (ferrie), etc. While the catalysts enumerated, with the exception of titanium tetrachlof ride, are solid at normal temperatures, they may bein liquid and/or vapor state under the conditions encountered in my process. Generally however I prefer to use such pressures that substantial vaporization of the catalyst Iis precluded.

- Under some circumstances however the catalyst may be largely or entirely vaporized in one or more steps in my process.

It is t'o bevunderstood that a-solid .or in situ type of catalyst may bev employed in which the Y catalyst remains in situ in the reaction zone, and liquid or vapor charge is passed through the zone. If the catalyst used is volatile at the temperatures and pressures employed, any portion of it so removed from the reaction zone may be trapped out, in the same way as that described for a slurry type catalyst. This recaptured catalyst may be in the form of a slurry and may be discarded but is preferably recirculated to the.

step from which it escaped.A Or it may be com-- mingled with any other slurry type catalyst from any other part of the system and thereafter used in slurry form. Any combination of solid-type and slurry-type catalyst may be used in the same or separate steps of my process. For example, the slurryformed by volatilization and condensation of solid catalyst in one or in two steps of the process may be zemployed exclusively in one Also', the charge stocks to any with either slurry or solid catalyst ilrst and then for further reaction introduced to a reaction zone containing the alternate type of catalyst. Thus, vapors entering the isomerization step may be introduced into an isomerization reaction zone in contact with slurry catalyst after which these vapors enter a second zone in which a solid type catalyst is maintained, the slurry employed in the iirst zone being made up of the catalyst volatilized from the second or solid catalyst zone.

Referring now to the accompanying drawing, cracking stock such as a medium petroleum distillate such as kerosene, gas oil, solar oil or the like is preheated to a temperature of say 750 F. to vaporize'it and is admitted via line Ito the cracking tower2. Through the tower 2 is circulated a cracking catalyst such as a metal halide in the form of a slurry or sludge derived from the alkylation unit 33 via line 40, the slurry passing through the preheatcr 3 into the tower 2 near its top via line 4. 'The catalystpasses downward .and exits from .the tower via line 5 and is returned to the heater and to the Vtower, to complete the cycle, a portion of it being removed continuously as spent via line 6. f

The hydrocarbon vapors are cracked while passing through the reaction zone, which in practice may be one or a series of towers, and the c'racked and uncracked vapors leave the tower via -line 1,

Vpass through the catalyst knock-out box 8 where any volatilized catalyst is condensedy and returned to the catalyst system. The vapors enter the A 'fractionator ill via line 9. From this tower I0 the ethane and propane are drawn oiT via line while the butanes, pentanes and hexanes are tak;

Yen oiias a sidestream via line` I3. A portion oi' head via line li5 to the feed to the aliylaticn unil-.-

are admitted via line 35 to the tower 33 at a plurality of vertically-spaced points. i

Used catalyst from the isomerizationsystem isl "pumped `continuously from line. 25 via line 3 6 through preheater31 and thence via line 38 into the'upper portion *oi the alkylation Vtower 33,

passes down through the tower and 'is returned for recycle through line 39. A portion of,this catalyst is withdrawn continuously through line 4 `and pumped to the cracking system to replacerthe `spent'catalyst withdrawn via line 6.

The alkylate formed in tower 33 passes through lli'ne 4I, catalyst knock-outbox 42, and line 43 t'o iractionator 44 whereit is separated from the un-v reacted material and is removed from'the system .through the line 45. Unreacted st ock isreturned vto recycle through the alkylation -towerthrough Normal and isomeric parailns of C4 to Ce'frorn j A an outsidesource may, if desired, be introduced 65 to the isomerization unit via line 48. Also iso- `paraiillns of C4 to Cs may be fed into the alkyla- `tion unit from an vetraneous source via line 49.

Ifdesired, although `less preferably, spent catalyst sludge orslurryleaving the isomerization 170 `unit 20 vmaybe passed directly into `the cracking `unit by means-i line 50 connecting line-36'to jline'49. f y

1 `Ii desired, .appropriate quantities o! anhydrous `aasigsoe c y troduced. into the isomerization unit 2li-via line l andfinto the alkylation unit 26 by the line 5 for expediting the reactions therein. t y

Fresh metal halide catalyst may be introduced via line 22'or line 41 in .the/ form of a slurry containing up to 80 percent of the metal halide, an oil similar to that being treated in isomerization unit I5 or alkylation unit 26'respectively being used toA make up the pumpable slurry.

33. f y l0 Likewise a'slurry of fresh metal halide catalyst Where the sidestream in line I3 is sufficiently in the crackingA feed mayr be introduced via line `high in iso-paraillns, tower I4 may be by-passed 40 to cracking unit I if desired. Also. oil simiby means of line I6 and the entire sidestream fed lar tothe cracking feed may be used in making. directly to alkyla'tion unit 33 4via line I5. Or the up the fresh catalystV slurry introduced. to the `entire sidestream may be by-passed around fracisomerization or alkylation units. .tionator I4 to the heater I8 by means of line I9. Preferable methods of carrying out 'this inven- In `the heater I8 the sidestream in line I3 or tion are described herein toV produce new and f the normal paraiiln bottom product leaving tower novel results and the invention is shown in sum- `I4' via line I9 is preheated to a temperature becient detail to .enable one skilled in the artto tween about 75 and about 425 F. and enters the 20 Dracticeit. It will be appreciated that in conisomerizing reaction zone,A tower 20,- at a point nectionwith the actual operation of any modinear its bottom, via line 2I. Fresh catalyst slurry flcation of my process-much conventional equip,- `is pumped to this system via line 22, is preheated ment not shown in the ilow diagram of the draw- 1to essentially the same temperature as that of the ing may need to be used and -may be readily incoming charge, in the heater 23and entersthe 25 supplied byone skilled in the art. Such equip- `tower near its top via line 24, leaving the tower vment will include pumps, heaters, coolers, catavia line 25 for recycling by mixing with the fresh lyst chambers, liractionating columns, refluxA @incoming catalyst. l j y lines, temperature controllers,' and the like. f

The visomerized hydrocarbons are transferred l Such equipment may be adapted in any particu--` through vapor line 2'6fto the catalyst knock-out 30 lar case by one skilled in the art with the benefit jbox 21, andthence pass'via line 29 to the iractionof the discussion and disclosures of the operaty lation unit 28 which maybe one or a series of ing conditions and `vmaterial flows given herein. towers, where the lower boiling isomers are sep- It will beappreciated that various modifications c larated from the high boiling straight-chain hymay be included without departing from the f drocarbons, the -latter being returned as recycle spirit of the invention. Itis emphasized, howvia line 39 tothe line I9. i ever, that this description is purely illustrative The isomerized" product passes via line 3| to and that the invention is not limited thereto, preheater 32 and thence entersl the alkylation but only by the terms and the spirit of theaptower 33 at the point 34 after being mixed .with a pended claims. f smal1 proportion of oleflns. The incoming oleflns 40' I claim: 1

1. A process which comprises subjecting a n petroleum oil ranging from naphtha to heavy gas oil to cracking with a metal halide-catalyst which has been spent for a, subsequent alkylation portion of said C4 to Cs hydrocarbons tothe iso' paraflin form, Aalkylating the C4 to Ca 'iso-parain hydrocarbons derived from said C toCe paraln hydrocarbons withlow molecular weightA olens y under substantially less severe conditions than said alkylatmg step and said alkylating step [being conducted under substantially less severe i conditions thanv said cracking step, and transferring said catalyst after it is substantially spent y for said isomerization step to said alkylating step and after it is substantially spent for said alkylating step to said cracking step.

petroleum oil ranging from to heavy gasoil tocracking'with a metal halide catalyst which has been spent for a subsequent alkylation if step. under' relatively severe vconditions to form substantial quantities of C4 toCs-'paraflin hydrocarbons, subjecting to catalytic 'isomerizationthe content of said C4 to -Ce paraflin hydrocarbons which' is capableoi forming more highly l, branched iso-paramns under relatively nild con- 4 ditions using a fresh metal halide catalyst which 3hydrogen chlorideorcther halide may be in; 751s the same as Ithat used inthe cracking step.

step, under relatively severe conditions to form steps; said ismerization step being conductedl y 2. A process which comprises 4subjecting a Y 

